spandrel

Compiled with AI assistance and selectively reviewed. Please consult the cited passages; the books remain the authoritative source. About this companion

Editorial synthesis · provisional

Definition

A spandrel is an evolutionary feature understood as a byproduct of other organization rather than a direct adaptation selected for that feature’s own function. RB1 invokes Gould and Lewontin against explaining every trait as an optimal solution. The concept does not deny natural selection, imply that every nonoptimal trait is a spandrel or establish that a byproduct can never later acquire a useful role.

Explanation

The direct paragraph places byproducts beside developmental viability, missing variation and historically good-enough outcomes. These are related limits on an all-purpose adaptation story, but they are not interchangeable diagnoses. The proposed entry preserves the narrower byproduct meaning instead of using spandrel for every unexplained or imperfect feature.

The native Gould–Lewontin reference supplies the attribution and architectural title. RB1 nevertheless retains natural selection as central to adaptive novelty, with constraints and random events also shaping what appears. A critical concept within evolutionary explanation therefore does not become a rejection of descent, inherited variation or differential reproduction.

The neighboring exaptation discussion concerns existing features finding new roles, while the spandrel classification concerns the feature’s origin as a byproduct. Keeping those questions separate avoids turning current usefulness into proof of original selection or making a byproduct permanently incapable of entering a later functional organization.

Scope and attribution

Keep byproduct origin distinct from adaptive explanation and possible later repurposing.

RB1 — The Real Book, Volume I: The Possible Is Real

The Gould–Lewontin byproduct concept qualifies rather than abolishes adaptive explanation.

Occurrence locators: 174, 175.

Background used in the editorial explanation

Named theories and mechanisms are distinguished from neighboring background, homonyms and the author’s own synthesis. Reproduced AI passages retain their separate voice.